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High Power Variable Resistor

IP.com Disclosure Number: IPCOM000080344D
Original Publication Date: 1973-Dec-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Miraglia, JA: AUTHOR

Abstract

This resistor is designed for high-current, low-voltage duty, especially where compactness and lockable adjustability are desired.

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High Power Variable Resistor

This resistor is designed for high-current, low-voltage duty, especially where compactness and lockable adjustability are desired.

The helical resistor element 10 is surrounded by an aluminum heat sink 12, which has an internal groove that matches the pitch and helix of resistor 10. The internal and end surfaces of heat sink 12 are coated with a high-dielectric material which insulates 10 from 12. Heat sink 12 has external grooves 13 so as to expose a maximum amount of surface area to air flow, which is the cooling medium.

During assembly, resistor 10, which has been brazed to the end terminal 14, is screwed into 12 so that terminal 14 is firmly seated against the dielectric coating on the end of heat sink 12. Wiper 16 is formed with a helix matching that of resistor 10 and is of a spring material so that the portion that contacts 10, which portion is cross-cut into quadrants, can track the surface of resistor 10 without binding due to thermal expansion. Located on the leading edge of the leading quadrant is a silver contact 18. The silver contact eliminates the possibility of resistance drift that may be caused by shifting of the point of contact, due to thermal cycling.

Bushing 20 is formed at one end to match the internal helix of resistor 10 and is bored at 22 so that it clears wiper 16, except in its slotted end portion 24. Bushing 20 has an external thread which permits it to be clamped against the resistor element 10 by a nut 2...